1. Field of the invention
The present invention is generally concerned with clutch release bearings, in particular those for automobile vehicles.
It is more particularly directed to so-called "pull" type clutch release bearings which are designed to operate in traction on the clutch release device of the clutch to be operated and which are coupled to this device for this purpose.
2. Description of the prior art
In some clutch release bearing assemblies, and in particular in the clutch release bearing assembly described in French Patent No. 2 304 826 and that described in U.S. patent application Ser. No. 916,805 of Oct. 8, 1986, now U.S. Pat. No. 4,733,762, it has been proposed to use between the clutch release bearing and the clutch release device to be operated, in order to couple the clutch release bearing to the clutch release device, a part referred to herein for convenience only as the "coupling part" or "action part" which, appropriately attached to the clutch release device, comprises on the side of the latter opposite the clutch release bearing a radial bearing flange through which it is adapted to bear axially on said clutch release device and thereby operate on it, and an axial bush which passes through said clutch release device, in cooperation with fastening means operative in traction between a coupling part of this kind and a part referred to herein for convenience only as the "drive part" forming part of the clutch release bearing, adapted to provide an axial coupling between said parts in the axial direction from the clutch release device to the clutch release bearing.
In practise the fastening means operative in traction employed generally comprise an annular coupling member, for example, as described in the forementioned U.S. patent application, a simple ring which is elastically deformable in the radial direction and which is carried by either of the parts to be fastened together in traction, and a substantially transverse drive bearing surface on the other of said parts and with which said annular coupling member cooperates in axial bearing engagement in the axial direction corresponding to the required axial coupling.
A particular advantage of an arrangement such as this is that it enables the clutch release device of the clutch to be operated to be fitted with the coupling part in advance, even before the corresponding clutch cover assembly is put together, and then, at the final assembly stage, the clutch release bearing to be engaged with the coupling part and thus with the clutch release device, by means of a simple clipping action.
At assembly time the drive part of the clutch release bearing is inserted axially into the coupling part and on such insertion the annular coupling member which is carried by one of said parts and which therefore, within the limits of a particular clearance or axial travel, is retained axially on the latter, is taken up by the other of said parts and, because of the action of the latter, which tends to entrain it although it is held back by the part which carries it, it is constrained to change from its normal or unstressed configuration to another, deployed or retracted configuration, in which it is engaged on or in the other of said parts until, once in line with the drive bearing surface of the latter, it assumes by virtue of its inherent elasticity a coupling configuration, which is not necessarily its initial unstressed configuration, but in which, having its drive bearing surface engaged with said part and with the part that carries it, it is adapted to provide the required axial coupling in traction of the two parts to each other when an axial drive movement in the reverse direction is applied to the clutch release bearing.
In practise, however, when it is in the ready position on the part which carries it the annular coupling member is not necessarily in the optimum position for the part which has to take it up.
To the contrary, it may by virtue of its own weight be situated off-axis relative to the latter.
Because of this, this part comes into contact with it only in the area which forms its upper part so that, because of the axial drive force that it applies to it, it tends to assume a slantwise position.
In the case of relatively small clutch release bearings, in which the annular coupling member is itself of relatively small diameter, any such slantwise disposition that may occur is usually insignificant.
The same is not true of relatively large size clutch release bearings in which the annular coupling member has a relatively large diameter.
In this case the slantwise disposition of the annular coupling member may lead to untimely jammming and, as a consequence of this, defective snap-fastening of it between the parts concerned.
Should this occur, the resulting assembly is defective and the corresponding operations have to be repeated.
To alleviate this problem consideration might be given to employing for the annular coupling member auxiliary spring centering means which either hold it elastically centered relative to the part which carries it, and spaced from the latter, or hold it elastically against a particular bearing surface on this part, for example a substantially frustoconical bearing surface, which systematically ensures that it is permanently centered relative to the latter.
However, the use of such auxiliary spring centering means inevitably results in some complexity of the assembly and, in particular, non-negligible manufacturing and assembly costs.
Consideration might also be given to providing the annular coupling member with lugs adapted to cooperate in bearing engagement with the part which carries it, so as to center it relative to the latter, for example by forming each of these lugs through localized arch or loop fashion deformation of the annular coupling member.
Even if the annular coupling member is initially disposed somewhat slantwise when taken up by the part comprising the drive bearing surface with which it has to cooperate, it is then systematically moved into a transverse plane by these lugs, being then correctly centered relative to this part.
For example, in order to achieve this result such lugs could cooperate with an edge of the part which carries it, either at one of the axial ends of the latter or by virtue of openings which are formed for them in the part concerned and through which they respectively pass, extending substantially radially.
However, in all cases it is necessary for the required centering to be achieved to obtain contact at three separate points appropriately distributed in the circumferential direction and the annular coupling member must therefore necessarily comprise three lugs.
In the case of a ring, for example, it is in practise difficult and therefore costly to form three lugs in this way on the ring.
Also, in the event that such lugs have to bear on a terminal edge of the part concerned, they must necessarily be offset in the axial direction relative to the main part of the annular coupling member on which they are provided, to the detriment of the overall axial dimension of the assembly.
A general object of the present invention is an arrangement adapted to provide satisfaction in a very simple way without any significant complication of the assembly or any particular increase in its overall axial dimension.